Brain Size


Size does not matter

it’s what you do with it that counts

Brain size, language and evolution

This article forms part of a large work on which I am currently engaged (August 2016). ‘Language and  Evolution’ is a subject that flowed from a course I took that studied the discovery of the remains of an extinct hominid called Homo floresiensis, in the Ling Bua cave on the island of Flores in Indonesia.  I tried to discover if this species could talk using a language. It is not possible to know from the archaeological evidence. I will be posting more from my studies of the development of human language through evolution, as sections are completed.

Scientific studies of early hominid skulls and other skeletal parts have provided some understanding of the sizes of brains of early humans, compared to those of modern people and some animals, including modern great apes.

What we do not yet understand, I would say, is the relationship between brain size and capabilities.  The brain governs what animals can do, how they can do it and how much they can learn in order to ‘know’ what to do. The brain is the repository of behavioural characteristics. Just having a small brain does not always indicate lack of behavioural characteristics. Species with smaller brains could still make some tools. Complex communication skills might also have been possible in hominids with relatively smaller brains. The skeletal remains can reveal quite a lot but not what the brain inside the bones could do. It seems fairly reasonable to conclude that Homo sapiens had a large brain, comparatively, and that he also could talk in a language.

Neanderthals left very little in the way of artistic artefacts and this suggests that symbolic thought was limited to a few individuals and not widespread in the species. Scientific work on how Neanderthals spoke suggests a more limited range of voiced sounds that we find in modern man.¹ The size of a brain is not the most important indicator of intelligence. The functionality of a brain comes from various elements including the spinal cord and brain stem; it also involves the nervous system and the extent to which the animal can see, hear and sense its surroundings (its cognitive abilities.) The behaviour of an animal will reflect its ability to learn from experience; the survival of a species, it can be said, is a function of its ability to learn quickly and to adapt to changes in its environment. I will discuss (below) how the acquisition of language increases the functionality of the brain and enhances a range of behaviours that stem from the brain’s capabilities.

But be careful –  brain size it not what you think.  Kendra Lechtenberg makes this point

The relationship between brain size and intelligence, both amongst humans and between different species, has never been particularly well-defined. Humans like to believe that our exceptional cognitive abilities must indicate that we are the kings of the animal kingdom in terms of brain size, or at least that we have the largest brains relative to our body size. As nature would have it, both of these common assumptions are incorrect. Whales and elephants have much bigger brains than humans, and we have about the same brain-to-body mass ratio as mice. Since it would be against human nature to admit defeat, scientists have crafted a third measure of brain size called the encephalization quotient, which is the ratio of actual brain mass relative to the predicted brain mass for an animal’s size (based off the assumption that larger animals require slightly less brain matter relative to their size compared to very small animals). By this metric, at least, humans come out on top, with an EQ of 7.5 far surpassing the dolphin’s 5.3 and the mouse’s measly 0.5.

As Kendra goes on to say ‘there is more to intelligence than brain size.’  The concept of intelligence is difficult; it is both controversial and troublesome. Many have challenged the credibility and accuracy of testing to provide a ‘intelligence quotient.’ What intelligence test measure is not the be all and end all of cognitive ability. When we are trying to analyse and discover how the brain has affected human evolution, we need to look at the whole picture of human functioning. Measuring the internal capacity of a cranium in litres is not really going to tell us all that much. As Alexandra Horowitz pointed out (Alexandra Horowitz, 2013) some animals appear to be smarter because they live in human environments but this is not always the case. As babies grow to adulthood, the size of their brain increases. But this does not give the whole picture; growth and development involve processes going on inside the brain with the growth of synapses. She writes

Consider, though, the strange case of that growing child. Every infant’s brain develops through a period of synaptogenesis—wanton proliferation of synapses, which are the connections between neurons—in the first year or so of life. But one could argue that it is when this intense brain growth ends that the real growth of the child qua individual begins. The next phase of brain development occurs in large part through an increase in synaptic pruning: paring of those connections that are not useful for perceiving, considering or understanding the world the child is facing. In this sense, it’s by downsizing that an individual’s brain is born.

It is possible to compare the mass of a brain with the mass of a body and to see if, on average, some animals – including humans – have a higher score than others. This itself does not answer the question about whether larger brain size co-relates with effective functioning. Many other factors come into play, not least, culture, social integration and knowledge. The intelligence of an individual is a product of how the brain cells work, how neural pathways are connected and many other factors that affect the level of function of the mind. If we want to consider how social groups function, mentally, we have to look at sociocultural factors alongside any analysis of the neurological functioning of the brain and its associated nervous system and cognitive behaviour. The individual Homo floresiensis might have had a comparatively small skull but we cannot conclude from that they were unintelligent. Simply measuring the capacity of its cranium is not going to tell us much. Viatcheslav Wlassoff (2015) commented

There are no doubts that the size of the human brain has increased tremendously in the last couple of million years, from around 600 cm3 in Homo habilis to an average of 1200 cm3 in Homo sapiens. The rise of our intelligence was most certainly linked with this increase of brain size… It is of great interest that the brain size of Neanderthals (1600 cm3) was much larger than in modern humans. We don’t know how Neanderthals would have performed in the IQ test, but we know that they were out-competed by Homo sapiens, even though Neanderthals were physically superior to our ancestors. It is quite likely that our higher level of intelligence played some role in this event.

A new insight into thinking (rather than just brains) comes from Christopher Bergland, (June 2016) who wrote

Fluid intelligence is the ability to think creatively, adapt to new situations, and solve problems you’ve often never encountered before in novel situations. Fluid intelligence generally involves the ability to use critical thinking—along with explicit and implicit knowledge—to identify patterns and connect-the-dots in a personal and original way. As Albert Szent-Györgyi once said, “Thus, the task is not to see what nobody has seen, but to think what nobody has thought, about what everybody sees.”

When it comes to the survival of the fittest and the evolution of human species, this idea of ‘fluid intelligence’ does seem to suggest how some individuals stepped up the ladder and became innovators and then made an impact on the life chances of the group as a whole. To take that iconic example, it was the man who discovered how to make fire that changed the course of human evolution.

This subject is also discussed in my feature article on Language and Evolution.

Notes and references

¹ The description of a Neanderthal hyoid from Kebara Cave (Israel) in 1989 fuelled scientific debate on the evolution of speech and complex language. Gross anatomy of the Kebara 2 hyoid differs little from that of modern humans. However, whether Homo neanderthalensis could use speech or complex language remains controversial. Similarity in overall shape does not necessarily demonstrate that the Kebara 2 hyoid was used in the same way as that of Homo sapiens. The mechanical performance of whole bones is partly controlled by internal trabecular geometries, regulated by bone-remodelling in response to the forces applied. Here we show that the Neanderthal and modern human hyoids also present very similar internal architectures and micro-biomechanical behaviours. Our study incorporates detailed analysis of histology, meticulous reconstruction of musculature, and computational biomechanical analysis with models incorporating internal micro-geometry. Because internal architecture reflects the loadings to which a bone is routinely subjected, our findings are consistent with a capacity for speech in the Neanderthals. [from http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082261%5D

also

It is possible to work out how Neanderthals may have spoken by reconstructing their vocal tracts and then comparing them with those of modern apes and modern humans.

The vocal tract’s structure is revealed in the base of the skull. Modern apes, such as chimpanzees, have a flat skull base and a high larynx whereas modern humans have an arched skull base and a low larynx. Our low larynx allows room for an extended pharynx and this structure enables us to produce the wide range of sounds we use in speech. Neanderthal skull bases appear to be less arched than those of modern humans but more arched than those of modern apes. This suggests that the Neanderthals would have been capable of some speech but probably not the complete range of sounds that modern humans produce.

and

Researchers studying Neanderthal genes discovered that they shared the same version of a gene FOXP2 with modern humans. FOXP2 is the only gene known so far that plays a key role in language. When mutated, it primarily affects language without affecting other
abilities. This gene appears in different forms in other vertebrates where it performs a slightly different function. This suggests the gene mutated not long before the split between the Neanderthals and modern human lines. However, there are plenty of genes involved in language so it takes more than the FOXP2 gene to prove a language ability.

and

The 90,000 year-old double burial from Jebel Qafzeh, Israel is one of the earliest that shows careful placement of the deceased. Burials of modern humans become increasingly complex over time, and Cro-Magnon burials usually include grave goods and other evidence of ritual activity. This pattern of behaviour is also seen at burial sites of other modern human cultures throughout the world.

[from Fran Dorey , Exhibition Project Coordinator http://australianmuseum.net.au/how-do-we-know-if-they-could-speak%5D

² Mesolithic (10,000-6000 years ago). At this period, there was still a hunter-gatherer culture, but a change in technology can be seen in the archaeological record. A different tool kit was now in use compared with that of the later Palaeolithic. For example, the bow and arrow were increasingly used. This is related to a change in the environment to a more temperate climate with increased woodland and disappearance of large grazing herds. Increases in the exploitation of aquatic resources and small game are also evident. Seasonal camp sites such as Star Carr (NE England) and Kelling Heath (Norfolk) have been excavated. Local adaptations to climate can be seen. Burial in the Mesolithic is characterized by a shift from single or small groups of burials to larger cemeteries in the open. No British examples of Mesolithic burials have been identified, with one possible exception. A disarticulated burial in a partially burnt log boat found at St. Albans has been dated to c.4,700 BC, so this could be late Mesolithic or Early Neolithic. … Burial practices in this period, although in open air flat cemeteries rather than caves, seem to continue the later Palaeolithic traditions of burial with the apparent importance of red ochre, ornaments of shell and teeth, and provision of tools and food. Does this mean that spiritual traditions also remained unchanged despite a change of lifestyle? [From http://www.spoilheap.co.uk/burial.htm%5D

³ Alan Fogel referred to in The Dynamic Dance: nonvocal communication in African great apes By Barbara J. KING, Barbara J King.

References

Mike Parker Pearson, Andrew Chamberlain, Oliver Craig, Peter Marshall, Jacqui Mulville, Helen Smith, Carolyn Chenery, Matthew Collins, Gordon Cook, Geoffrey Craig, Jane Evans, Jen Hiller, Janet Montgomery, Jean-Luc Schwenninger, Gillian Taylor and Timothy Wess (2005). Evidence for mummification in Bronze Age Britain. Antiquity, 79, pp 529-546.

Stockhammer PW, Massy K, Knipper C, Friedrich R, Kromer B, Lindauer S, et al. (2015) Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating.

Wrangham, R. & Carmody, R. Human adaptation to the control of fire. Evol. Anthropol. 19(5), 187–199 (2010).

Maev Kennedy, The Guardian, ‘A bronze age Pompeii’: archaeologists hail discovery of Peterborough site, 12th January 2016.

John Novembre, Nature 522, 164–165 (11 June 2015), Human evolution: Ancient DNA steps into the language debate.

Kendra Lechtenberg (2014) writing in Stanford Neurosciences Institute, https://neuroscience.stanford.edu/news/ask-neuroscientist-does-bigger-brain-make-you-smarter

Alexandra Horowitz, 2013, Smithsonian Magazine, Why Brain Size Doesn’t Correlate With Intelligence – We can nurture growth, but never really control it. [from:  http://www.smithsonianmag.com/science-nature/why-brain-size-doesnt-correlate-with-intelligence-180947627/#KbJqgMbq8G7W60cK.99

Viatcheslav Wlassoff, 2015, Is There an Association Between Brain Size and Intelligence? from http://brainblogger.com/2015/11/22/is-there-an-association-between-brain-size-and-intelligence/

Christopher Bergland, June 2016, Superfluidity: Fluid Intelligence Goes Beyond Brain Size, Psychology Today.  From https://www.psychologytoday.com/blog/the-athletes-way/201606/superfluidity-fluid-intelligence-goes-beyond-brain-size